Image capture apparatus and control method thereof

ABSTRACT

An image capture apparatus with a pre-capture function for generating still image data pieces at a predetermined interval during a pre-capture period between detection of a first shooting instruction and detection of a second shooting instruction, is disclosed. The apparatus determines, within the pre-capture period, a period in which one or more pre-captured still image data pieces are to be recorded in association with a still image data piece generated in response to the detection of the second shooting instruction. The period is determined based on a difference between (i) a time of the detection of the first shooting instruction, or a shooting time of an image data piece selected by a user from among the pre-captured still image data pieces, and (ii) a time of the detection of the second shooting instruction.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an image capture apparatus and acontrol method thereof.

Description of the Related Art

It has been known that an image capture apparatus, such as a digitalcamera, has a pre-capture function of starting recording of capturedimages from before a shooting instruction is input (Japanese PatentLaid-Open No. 2002-252804).

In a case where the pre-capture function is enabled, image data forrecording is periodically generated during a pre-capture period frominputting of a shooting preparation instruction (e.g., an operation ofdepressing a shutter button halfway) to inputting of a shootinginstruction (e.g., an operation of fully depressing the shutter button).Then, the image data pieces generated during the pre-capture period arerecorded in addition to image data obtained in accordance with inputtingof the shooting instruction.

Conventionally, all the image data pieces generated during thepre-capture period are recorded unconditionally and thus the capacity ofa recording medium may be consumed significantly. Furthermore, aninterval at which the image data is generated during the pre-captureperiod is constant, the interval may not be appropriate for a movingsubject in some cases.

In view of the foregoing problems with conventional techniques, thepresent invention according to an embodiment thereof provides an imagecapture apparatus and a control method thereof that can flexiblycontrol, for example, the number of image data pieces recorded using apre-capture function and the interval of obtainment of the image datapieces.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided animage capture apparatus with a pre-capture function for generating stillimage data pieces at a predetermined interval between detection of afirst shooting instruction and detection of a second shootinginstruction, the image capture apparatus comprising: one or moreprocessors that execute a program stored in a memory and therebyfunction as: a control unit that determines, within a period in whichthe pre-capture function was performed, a period in which one or morestill image data pieces generated through the pre-capture function areto be recorded in association with a still image data piece generated inresponse to the detection of the second shooting instruction, based on adifference between (i) a time of the detection of the first shootinginstruction, or a shooting time of an image data piece selected by auser from among the still image data pieces generated through thepre-capture function, and (ii) a time of the detection of the secondshooting instruction.

According to another aspect of the present invention, there is provideda control method executed by an image capture apparatus with apre-capture function for generating still image data pieces at apredetermined interval between detection of a first shooting instructionand detection of a second shooting instruction, the control methodcomprising: determining, within a period in which the pre-capturefunction was performed, a period in which one or more still image datapieces generated through the pre-capture function are to be recorded inassociation with a still image data piece generated in response to thedetection of the second shooting instruction, based on a differencebetween (i) a time of the detection of the first shooting instruction,or a shooting time of an image data piece selected by a user from amongthe still image data pieces generated through the pre-capture function,and (ii) a time of the detection of the second shooting instruction.

According to further aspect of the present invention, there is provideda non-transitory computer-readable medium that stores a program forcausing a computer included in an image capture apparatus to execute acontrol method of the image capture apparatus, wherein the image captureapparatus has a pre-capture function for generating still image datapieces at a predetermined interval between detection of a first shootinginstruction and detection of a second shooting instruction, and whereinthe control method comprises: determining, within a period in which thepre-capture function was performed, a period in which one or more stillimage data pieces generated through the pre-capture function are to berecorded in association with a still image data piece generated inresponse to the detection of the second shooting instruction, based on adifference between (i) a time of the detection of the first shootinginstruction, or a shooting time of an image data piece selected by auser from among the still image data pieces generated through thepre-capture function, and (ii) a time of the detection of the secondshooting instruction.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an exemplary functional configurationof a camera system according to an embodiment.

FIG. 2 is a schematic diagram for describing the operations of thecamera system according to an embodiment.

FIG. 3 is a flowchart showing the operations of a main body 100according to a first embodiment.

FIG. 4 is a flowchart showing the operations of the main body 100according to a second embodiment.

FIG. 5 is a flowchart showing the operations of the main body 100according to a third embodiment.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments are described in detail with reference to theattached drawings. Note, the following embodiments are not intended tolimit the scope of the claimed invention. Multiple features aredescribed in the embodiments, but limitation is not made to an inventionthat requires all such features, and multiple such features may becombined as appropriate. Furthermore, in the attached drawings, the samereference numerals are given to the same or similar configurations, andredundant description thereof is omitted.

Note that the following embodiments are described in relation to a casewhere the present invention is implemented on an interchangeable-lensdigital camera. However, the present invention can be also implementedon no particular electronic devices that have an image capture function.Such electronic devices include a video camera, a computer device (apersonal computer, a tablet computer, a media player, a PDA, and soforth), a mobile telephone device, a smartphone, a game device, a robot,a drone, and a driving recorder. These are examples, and the presentinvention can be implemented on other electronic devices.

First Embodiment

FIG. 1 is a block diagram showing an exemplary functional configurationof a camera system according to an embodiment of the present invention.The camera system includes a main body 100 and a lens unit 200. Althoughthe lens unit 200 is attachable to and removable from the main body 100in the present embodiment, the lens unit 200 may be integrated with themain body 100.

The lens unit 200 includes a mount unit 202 that is mechanicallyattachable to and removable from a mount unit 102 of the main body 100.Also, the lens unit 200 and the main body 100 are capable ofcommunicating with each other via contact points 201 and 101, which comeinto contact with each other when the lens unit 200 is mounted on themain body 100. Furthermore, electric power that enables the lens unit200 to operate is supplied from the main body 100 to the lens unit 200via the contact points 201 and 101.

The lens unit 200 includes an imaging optical system 205, a diaphragm203, and a lens control unit 204. The imaging optical system 205includes a plurality of lenses including a focusing lens, and forms anoptical image on an image capture surface of an image sensor 105. Thediaphragm 203 adjusts the amount of light incident from the lens unit200 to the main body 100 by way of the aperture size. The lens controlunit 204 drives the focusing lens and the diaphragm 203 of the imagingoptical system 205 under control of a system control unit 150.

The lens control unit 204 includes, for example, a processor capable ofexecuting programs, and memories (a ROM and a RAM). The lens controlunit 204 realizes the functions of the lens unit 200 by loading theprograms stored in the ROM to the RAM and executing the programs usingthe processor. The ROM stores not only the programs, but also constantsand variables for the operations, as well as unique information (e.g., aserial number), management information (e.g., a product name), functioninformation (e.g., a maximum aperture, a minimum aperture, and a focallength), current and past setting values, and the like of the lens unit200.

In response to a request from the system control unit 150, the lenscontrol unit 204 transmits information of the lens unit 200 (informationstored in the ROM, and information indicating the current state (theaperture, the position of the focusing lens, and so forth)) to thesystem control unit 150. Furthermore, in response to a request from thesystem 150, the lens control unit 204 drives the diaphragm 203, and thefocusing lens of the imaging optical system 205.

In the main body 100, a shutter 103 is a mechanical shutter, andcontrols an exposure period of the image sensor 105. Under control ofthe system control unit 150, a shutter control unit 104 controls theopening/closing operation of the shutter 103.

The image sensor 105 may be a known CCD or CMOS color image sensorincluding, for example, color filters based on the primary-color Bayerarray. The image sensor 105 includes a pixel array in which a pluralityof pixels are arrayed two-dimensionally, and peripheral circuits forreading out signals from the pixels. In each pixel, chargescorresponding to the amount of incident light are accumulated throughphotoelectric conversion. A signal having a voltage corresponding to theamount of charges accumulated during an exposure period is read out fromeach pixel; as a result, a group of pixel signals (analog image signals)indicating an optical image formed by the image capture optical system205 on the image capture surface is obtained. The analog image signalsare supplied to an image processing circuit 106.

The image processing circuit 106 applies pre-set image processing to theanalog image signals, thereby generating signals and image datacorresponding to the intended use, and obtaining and/or generatingvarious types of information. The image processing circuit 106 may be,for example, a dedicated hardware circuit designed to realize specificfunctions, such as an Application Specific Integrated Circuit (ASIC).Alternatively, the image processing circuit 106 may be configured torealize specific functions as a result of a processor, such as a DigitalSignal Processor (DSP) and a Graphics Processing Unit (GPU), executingsoftware.

The image processing applied by the image processing circuit 106 caninclude, for example, preprocessing, color interpolation processing,correction processing, detection processing, data editing processing,evaluation value calculation processing, special effects processing, andthe like.

The preprocessing can include A/D conversion, signal amplification, baselevel adjustment, defective pixel correction, and the like.

The color interpolation processing is executed in a case where the imagesensor 105 includes color filters, and is processing for interpolatingthe values of color components that are not included in discrete pixeldata pieces that compose image data. The color interpolation processingis also referred to as demosaicing processing.

The correction processing can include processing such as white balanceadjustment, tone correction, correction of image deterioration caused byoptical aberration of the imaging optical system 101 (image recovery),correction of the influence of vignetting of the image capture opticalsystem 101, correction of the influence of vignetting of the imagecapture optical system 205, color correction, and the like.

The detection processing can include detection of a characteristicregion (e.g., a face region and a human body region) and movementsthereof, processing for recognizing a person, and the like.

The data editing processing can include processing such as composition,scaling, encoding and decoding, and generation of header information(generation of a data file). The data editing processing also includesgeneration of image data for display and image data for recording.

The evaluation value calculation processing can include processing suchas generation of signals and evaluation values used in automatic focusdetection (AF), and generation of evaluation values used in automaticexposure control (AE).

The special effects processing can include, for example, processing suchas addition of blur effects, changing of tones, and relighting.

Note that these are examples of processing that can be applied by theimage processing circuit 106, and do not limit processing applied by theimage processing circuit 106.

A recording medium 107 is, for example, a semiconductor memory card.Still image data and moving image data for recording generated by theimage processing circuit 106 are recorded into the recording medium 107by the system control unit 150.

A display unit 111 is, for example, a liquid crystal display (LCD). Thedisplay unit 111 functions as an electronic viewfinder (EVF) bydisplaying live view images. Also, the display unit 111 displays a GUIsuch as a menu screen, image data recorded in the recording medium 107,and the like. The display unit 111 may be a touch display.

A temperature sensors 121 are disposed in a plurality of areas of themain body 100, and supply a signal indicating a temperature therearoundto the system control unit 150.

An operation unit 124 is a collective term for input devices (buttons,switches, dials, and the like) that have been provided to enable a userto input various types of instructions to the main body 100, except fora shutter button 126 and a power switch 125. The input devices thatcompose the operation unit 124 have names corresponding to the allocatedfunctions. For example, the operation unit 124 includes a moving imagerecording switch, a shooting mode selection dial for selecting ashooting mode, a menu button, directional keys, a determination key, andthe like. Note that the functions allocated to the same input device maybe variable. Also, the input devices may be software buttons or keysthat use a touch display. Furthermore, input devices that do not requiremechanical operations, such as an eye-gazing input device and soundinput device, may be used.

The power switch 125 switches between a state where a power control unit160 supplies electric power to the main body 100 (power ON) and a statewhere no electric power is supplied thereto (power OFF). Note that theremay be a constituent element to which electric power is supplied evenduring the power OFF state.

The shutter button 126 is a button for recording still images, andincludes a switch (SW1) 127 that is turned ON by a halfway-depressionoperation, and a switch (SW2) 128 that is turned ON by a full-depressionoperation.

The system control unit 150 monitors the operation unit 124; itrecognizes depression of the moving image recording switch in a shootingstandby state as a recording start instruction for moving images, andrecognizes depression of the moving image recording switch during therecording of moving images as a recording stop instruction.

The system control unit 150 is, for example, a processor capable ofexecuting programs. The system control unit 150 controls the operationsof the main body 100 and the lens unit 200 by reading in programs storedin a nonvolatile memory 140 to a system memory 123 and executing theprograms. The control performed by the system control unit 150 realizesvarious functions of the camera system.

The system control unit 150 recognizes the act of turning ON the SW1 127as a shooting preparation instruction (a first shooting instruction),and the act of turning ON the SW2 128 as a shooting start instruction (asecond shooting instruction). Upon detecting the shooting preparationinstruction, the system control unit 150 performs an operation ofdetermining exposure conditions (AE) and an operation of automatic focusdetection (AF) of the lens unit 200, and waits for the shooting startinstruction. Also, in a case where a pre-capture function is enabled,the system control unit 150 starts pre-capture in response to thedetection of the shooting preparation instruction.

The nonvolatile memory 140 is, for example, electrically rewritable, andstores programs to be executed by the system control unit 150, varioustypes of setting values of the main body 100, GUI data, and so forth.

The system memory 123 is, for example, a RAM, and is a main memory thatis used by the system control unit 150 when executing programs. A partof the system memory 123 is used as a video memory for the display unit111, and used as a data buffer memory.

A system timer 122 measures a period set by the system control unit 150,and provides a clock function.

A wireless communication circuit 129 includes a transmission/receptioncircuit conforming to one or more of predetermined wirelesscommunication standards (e.g., a wireless LAN and Bluetooth®)). The mainbody 100 can receive a shooting instruction from an external deviceconnected via the wireless communication circuit 129. Also, in thenonvolatile memory 140, a delay period that should be taken intoconsideration in relation to communication via the wirelesscommunication circuit 129 is stored for each communication standard.

A power unit 170 is a power source capable of supplying electric powerto the main body 100, such as a battery and an AC adapter.

The power control unit 160 includes a battery detection circuit, aprotection circuit, a DC-DC converter, an LDO regulator, and so forth,and supplies electric power from the power unit 170 to the camera systemin a form suitable to the supply destination. The power control unit 160detects, for example, the type of the power unit 170, and the type andthe remaining level of a mounted battery. Also, the power control unit160 blocks electric power from the power unit 170 in a case whereovercurrent has been detected.

FIG. 2 is a schematic diagram for describing the operations of thesystem control unit 150 related to the pre-capture function. Acommunication unit 152 and a determination unit 151 included in thesystem control unit 150 are functions which are realized by theprocessor executing programs, and which are represented as a pluralityof function blocks in order to facilitate the description andunderstanding.

The communication unit 152 communicates with function blocks connectedto the system control unit 150. The determination unit 151 controls theoperations of the main body 100 and the lens unit 200 based oninformation obtained via the communication unit 152.

As stated earlier, in the present embodiment, when the SW1 127 is turnedON by the operation of depressing the shutter button 126 halfway,shooting preparation operations for a still image are executed, and inaddition to this, pre-capture is started. Note that in the pre-capture,one of the following may be performed: (1) record still image data forrecording that has been generated by the image processing circuit 106from moving image frames that have been obtained for the purpose oflive-view display in the shooting standby state; and (2) start anoperation of continuously shooting still images using an electronicshutter or the shutter 103, and record still image data for recordingthat has been generated by the image processing circuit 106. In the caseof (1), there is a case where the resolution of still images recorded inthe pre-capture is lower than the resolution of a still image recordedwhen the shutter button 126 is fully depressed. Also, in the case of(2), there is a case where live-view display is not performed during thepre-capture.

Note that the system control unit 150 (communication unit 152) storesstill image data that has been generated through the pre-capture to thesystem memory 123, with time information obtained from the system timer122 added thereto. The communication unit 152 updates still image datawithin a buffer so that the most recent still image data correspondingto a predetermined period or number of frames is buffered in the systemmemory 123 while using a period or the number of frames corresponding toa preset buffer capacity as a limit.

When the SW2 128 is turned ON by the operation of fully depressing theshutter button 126, the determination unit 151 ends the pre-capture, andexecutes a still image shooting operation. Then, the determination unit151 adds time information obtained from the system timer 122 to stillimage data for recording that has been generated by the image processingcircuit 106, and then records the still image data for recording,together with the pre-captured still image data, into the recordingmedium 107. In the present embodiment, every still image data piece thathas been pre-captured is not recorded unconditionally, but the number offrames to be recorded is reduced in view of the tendency of thephotographer.

Using a flowchart of FIG. 3 , the following describes a still imageshooting operation that accompanies the pre-capture according to thepresent embodiment. Here, it is assumed that the camera system is in theshooting standby state, and is monitoring operations on the shutterbutton 126 while performing live-view display on the display unit 111.

In step S100, the system control unit 150 determines whether the firstshooting instruction (ON of the SW1 127) has been detected; step S101 isexecuted when it is determined that the first shooting instruction hasbeen detected, and step S100 is repeatedly executed when it is notdetermined that the first shooting instruction has been detected.

In step S101, the system control unit 150 obtains current timeinformation from the system timer 122, and stores the same to the systemmemory 123 as the time of the first shooting instruction. Also, thesystem control unit 150 starts a pre-capture operation. Accordingly, theimage processing circuit 106 starts generating pre-captured still imagedata pieces for recording. The pre-captured still image data piecesinclude shooting time information obtained from the system timer 122added thereto, and are sequentially buffered in the system memory 123.

In step S102, the system control unit 150 determines whether the secondshooting instruction (ON of the SW2 128, or an input from an externalapparatus) has been detected; step S103 is executed when it isdetermined that the second shooting instruction has been detected, andstep S102 is repeatedly executed when it is not determined that thesecond shooting instruction has been detected.

In step S103, the system control unit 150 obtains current timeinformation from the system timer 122, and stores the same to the systemmemory 123 as the time of the second shooting instruction. Note that ina case where the second shooting instruction has been received from anexternal apparatus, the system control unit 150 obtains, from thenonvolatile memory 140, a delay amount corresponding to the standardthat is used in wireless connection to the external apparatus, correctsthe time of the second shooting instruction, and stores the correctedtime to the system memory 123. Specifically, the system control unit 150corrects the time of the second shooting instruction to the timeobtained by subtracting the delay amount from the time obtained from thesystem timer 122.

Also, the system control unit 150 stops the pre-capture operation, andexecutes a still image shooting (main shooting) operation based on thesecond shooting instruction. A still image data piece for recordingpertaining to the present shooting, which has been generated by theimage processing circuit 106, includes the time of the second shootinginstruction added thereto, and is buffered in the system memory 123.Thereafter, the system control unit 150 records the pre-captured stillimage data pieces and the still image data piece pertaining to thepresent shooting, which have been buffered in the system memory 123,into the recording medium 107 in association with one another.

In step S104, the system control unit 150 displays a list of reducedimages (e.g., thumbnail images) based on the still image data piecesrecorded in step S103 on the display unit 111 in a selectable manner,and causes the user to select an image that is desired to be stored.

In step S105, the system control unit 150 determines whether an imagehas been selected, via an operation on the operation unit 124, from thedisplayed list. The system control unit 150 executes step S106 when itis determined that an image has been selected, and repeatedly executesstep S105 when it is not thus determined. The operation of selecting animage may be any known operation, such as a touch operation on a reducedimage, and an operation that uses a cursor. Note that a selection of aplurality of images may be permitted.

In step S106, the system control unit 150 obtains shooting timeinformation from the still image data piece corresponding to theselected image, and stores the shooting time information to the systemmemory 123. Also, the system control unit 150 stores the oldest timeamong the obtained times to the nonvolatile memory 140.

In step S107, the system control unit 150 determines whether thepre-capture was performed in the past. In a case where one or moreshooting times are stored in the nonvolatile memory 140, the systemcontrol unit 150 determines that the pre-capture was performed in thepast, and executes step S108.

Also, in a case where a shooting time is not stored in the nonvolatilememory 140, the system control unit 150 determines that the pre-capturewas not performed in the past, and executes step S111. In this case, theperiod for which the pre-capture is performed, or the number of framesto be pre-captured, is not changed.

In step S108, the system control unit 150 obtains the time of the firstshooting instruction, the time of the second shooting instruction, andthe old shooting time of the image selected in step S104 from thenonvolatile memory 140.

In step S109, the system control unit 150 calculates an evaluation valuebased on the times obtained in step S108. The evaluation value may be,for example, one of the following.

(1) An average value of the difference between the time of the secondshooting instruction and the time of the first shooting instruction

(2) A variation (variance or standard deviation) in the differencebetween the time of the second shooting instruction and the time of thefirst shooting instruction

(3) An average value of the difference between the time of the secondshooting instruction and the shooting time of the selected image

(4) A variation (variance or standard deviation) in the differencebetween the time of the second shooting instruction and the shootingtime of the selected image

Provided that the calculated time difference is x, the number of samplesof x is n, and the average value of the samples is x, the standarddeviation s is derived as follows.

$s = \sqrt{\frac{1}{n}*{\sum\limits_{i = 1}^{n}\left( {x_{i} - \overset{\_}{x}} \right)^{2}}}$

Then, the system control unit 150 determines whether the shootingsettings related to the pre-capture are to be changed based on thecalculated evaluation value; step S110 is executed in a case where it isdetermined that the shooting settings are to be changed, and step S111is executed in a case where it is determined that the shooting settingsare not to be changed.

Here, as one example, the system control unit 150 determines that theshooting settings related to the pre-capture are to be changed when theevaluation value is equal to or larger than a predetermined value(threshold) that has been set in advance, and determines that theshooting settings related to the pre-capture are not to be changed whenthe evaluation value is smaller than the threshold. Note that differentpredetermined values can be used for different evaluation values.

The system control unit 150 can determine that the shooting settingsrelated to the pre-capture are to be changed, for example, in a casewhere the evaluation value (1) is equal to or longer than one minute, orin a case where the evaluation value (4) (standard deviation) is equalto or longer than 30 seconds.

In step S110, the system control unit 150 changes the settings relatedto the pre-capture. For example, the system control unit 150 makes thechange so that, among the image data pieces obtained during thepre-capture period, only the image data pieces obtained during a periodbased on the average value of the difference between the shooting timeof the selected image and the time of the second shooting instructionare recorded.

The difference between the shooting time of the selected image and thetime of the second shooting instruction reflects a time difference(response time) between the timing at which the user determined toperform the shooting and the time when the shutter button 126 wasactually depressed fully, and is considered to be information unique tothe user. Therefore, recording the image data pieces obtained during aperiod based on the average value of this time difference makes itpossible to reduce the consumption of the capacity of the recordingmedium 107 caused by recording of image data pieces that are not desiredby the user, while increasing the possibility of recording of image datapieces desired by the user.

As one example, the system control unit 150 can make the change so as torecord only the image data pieces obtained during a period obtained bysubtracting (the sum of the average value of the difference between theshooting time of the selected image and the time of the second shootinginstruction, and the standard deviation of the difference) from the timeof the second shooting instruction. In this way, presuming that the timedifference is normally distributed, the image data pieces desired by theuser are recorded with a probability of approximately 70%. Note thatalthough the period obtained by subtracting the sum of the average valueof the difference and the standard deviation of the difference is usedhere, it is permissible to use a range obtained by subtracting the sumof the average value of the difference and a multiple (equal to orlarger than one-fold, and equal to or smaller than two-fold) of thestandard deviation of the difference.

In step S111, the system control unit 150 deletes, from the recordingmedium 107, unnecessary image data pieces that are included among thestill image data pieces recorded in step S103. In a case where thetransition has been made, for example, from step S107 or S109 to stepS111, the unnecessary image data pieces may be still image data piecesthat have not been selected on a screen displaying the list. On theother hand, in a case where the transition has been made from step S110to step S111, the unnecessary image data pieces may be image data pieceswhich are included among the still image data pieces recorded in stepS103 and which are not included in the period changed in step S110. Notethat the deletion in step S111 may not be performed.

The period changed in step S110 is reflected at the time of the nextshooting, thereby changing the amount of still image data piecesrecorded in step S103.

(Exemplary Modifications)

In step S110, the period for which image data pieces are recorded duringthe pre-capture period is changed; however, the interval of obtainmentof image data pieces may further be changed. For example, the intervalof obtainment of still image data pieces for recording can be shortened(the frequency of the obtainment is increased) in a case where thelength of the period for which image data pieces are recorded that waschanged in step S110 is equal to or shorter than a predetermined length,or in a case where the evaluation value is smaller than thepredetermined value. As a result, the shooting interval is shortened,and more fine-tuned pre-capture can be realized, thereby increasing thepossibility of obtainment of images that match the user's intentionthrough the pre-capture.

Furthermore, for example, in comparing the interval of obtainment ofimage data pieces in one of the following periods, which have beendescribed earlier, with the interval of obtainment of image data piecesoutside these periods, the change may be made so as to increase theinterval of obtainment of (reduce the frequency of obtainment of) imagedata pieces outside these periods:

(1) A period based on the average value of the difference between theshooting time of the selected image and the time of the second shootinginstruction;

(2) A period obtained by subtracting (the sum of the average value ofthe difference between the shooting time of the selected image and thetime of the second shooting instruction, and the standard deviation ofthe difference) from the time of the second shooting instruction; and

(3) A period obtained by obtained by subtracting the sum of the averagevalue of the difference and a multiple (equal to or larger thanone-fold, and equal to or smaller than two-fold) of the standarddeviation of the difference.

As a result, the number of frames of image data pieces outside theseperiods is reduced; this can reduce the consumption of the capacity ofthe recording medium 107 caused by recording of image data pieces thatare not desired by the user.

Note that in a case where the length of the period has been changed instep S110, the number of frames of image data pieces obtained at theshortened obtainment interval should not exceed the number of frames ofimage data pieces obtained during the length of the period before thechange in step S110. Furthermore, the obtainment interval is shortenedso that there is no shortage in the amount of exposure for the obtainedimage data pieces.

As described above, according to the present embodiment, the period forwhich the obtained image data pieces are to be recorded during thepre-capture period is changed based on the difference between theshooting time of the image selected by the user and the time of thesecond shooting instruction. This enables recording of only the imagedata pieces that were obtained in a period in which the user'scharacteristics are reflected during the pre-capture period, andunnecessary consumption of the storage capacity of the recording mediumand electric power can be suppressed.

Furthermore, in a case where the length of the changed period is equalto or shorter than the predetermined length, the pre-capture can beperformed at a more fine-tuned time interval by increasing the intervalof obtainment of image data pieces.

Second Embodiment

Next, a second embodiment of the present invention is described using aflowchart shown in FIG. 4 . The present embodiment can be implementedfollowing step S103 of the first embodiment. After image data has beenrecorded into the recording medium 107 in response to the secondshooting instruction, the system control unit 150 obtains the setting ofthe frame rate (obtainment interval) of the pre-capture from, forexample, the nonvolatile memory 140 in step S302.

In step S303, the system control unit 150 calculates a time differencebetween the time of the first shooting instruction and the time of thesecond shooting instruction. Furthermore, the system control unit 150determines whether the calculated time difference is equal to or longerthan a predetermined period that has been set in advance. It is assumedhere that the predetermined period is, for example, 30 seconds. Thesystem control unit 150 executes step S304 when it is determined thatthe time difference is equal to or longer than the predetermined period,and ends processing without changing the frame rate of the pre-capturewhen it is not thus determined.

In step S304, the system control unit 150 determines whether the framerate of the pre-capture obtained in step S302 is equal to or higher thana threshold (e.g., 20 fps); processing proceeds to step S305 when it isdetermined that the frame rate of the pre-capture is equal to or higherthan the threshold, and processing is ended without changing the framerate of the pre-capture when it is not thus determined. Thisdetermination may be a determination of whether the interval at whichstill image data pieces are generated using the pre-capture function islower than a threshold.

In step S305, the system control unit 150 reduces the frame rate of thepre-capture (to, for example, 10 fps) (increases the interval at whichstill image data pieces are generated).

In step S306, the system control unit 150 thins out (deletes) image datapieces which are included among the image data pieces recorded into therecording medium 107 in step S103 and which were obtained through thepre-capture, so as to achieve the reduced frame rate.

According to the present embodiment, in a case where the time differencebetween the time of the first shooting instruction and the time of thesecond shooting instruction has a length equal to or longer than apredetermined value, the capacity of the recording medium 107 can besaved by reducing the frame rate of image data pieces recorded throughthe pre-capture.

Note that the present embodiment may be combined with the firstembodiment, and processing of step S104 onward of FIG. 3 may be executedfollowing the flowchart of FIG. 4 .

Third Embodiment

Next, a third embodiment of the present invention is described using aflowchart shown in FIG. 5 . The present embodiment can be executed atthe time of standby for shooting, prior to processing of the flowchartof FIG. 3 that has been described in the first embodiment.

In step S501, the system control unit 150 obtains the result of subjectdetection processing that has been executed by the image processingcircuit 106 with respect to images for live-view display.

In step S502, the system control unit 150 determines whether a pre-setsubject has been detected through the subject detection processing; stepS503 is executed when it is determined that the predetermined subjecthas been detected, and processing from step S100 is executed withoutchanging the frame rate of the pre-capture when it is not thusdetermined.

Here, the pre-set subject is a movable subject, and examples thereofinclude a person, an animal, an insect, a vehicle, a flying object, andso forth.

In step S503, the system control unit 150 sets (changes) the frame rateof the pre-capture in accordance with the type of the detected subject.Specifically, the frame rate is set so that it increases as the speed atwhich the subject can move increases. A relationship between the subjecttypes and the speeds at which the subject can move can be registered in,for example, the nonvolatile memory 140 in advance.

For example, frame rates can be registered in accordance with thefollowing magnitude relationship: a subject represented by a person, aninsect, or an animal<a subject represented by a vehicle<a subjectrepresented by a flying object. Note that this is one example, and framerates may be registered in correspondence with more detailed categories,respectively; for instance, the frame rate corresponding to a subjectrepresented by an animal may vary depending on the type of the animal.The number of categories of subjects can vary depending on, for example,the subject detection capability of the image processing circuit 106.

In the present embodiment, by setting the frame rate of the pre-capturein accordance with a detected subject, the pre-capture can be executedat a shooting interval appropriate for the subject. This can increasethe possibility that a subject can be pre-captured at a timing intendedby the user. Furthermore, setting of an excessive frame rate for asubject can be avoided, and an increase in the amount of image dataattributed to the pre-capture can be suppressed.

OTHER EMBODIMENTS

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully asanon-transitory computer-readable storage medium′) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2022-25605, filed on Feb. 22, 2022, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An image capture apparatus with a pre-capturefunction for generating still image data pieces at a predeterminedinterval between detection of a first shooting instruction and detectionof a second shooting instruction, the image capture apparatuscomprising: one or more processors that execute a program stored in amemory and thereby function as: a control unit that determines, within aperiod in which the pre-capture function was performed, a period inwhich one or more still image data pieces generated through thepre-capture function are to be recorded in association with a stillimage data piece generated in response to the detection of the secondshooting instruction, based on a difference between (i) a time of thedetection of the first shooting instruction, or a shooting time of animage data piece selected by a user from among the still image datapieces generated through the pre-capture function, and (ii) a time ofthe detection of the second shooting instruction.
 2. The image captureapparatus according to claim 1, wherein the control unit determines theperiod in which one or more still image data pieces generated throughthe pre-capture function are to be recorded using the difference at thetime of past execution of the pre-capture function.
 3. The image captureapparatus according to claim 2, wherein the control unit determines theperiod in which one or more still image data pieces generated throughthe pre-capture function are to be recorded based on an average value ofthe differences.
 4. The image capture apparatus according to claim 2,wherein the control unit determines, as the period in which one or morestill image data pieces generated through the pre-capture function areto be recorded, a period between the time of the detection of the secondshooting instruction and a time that is backward from the time when thesecond shooting instruction is detected by the average of thedifferences.
 5. The image capture apparatus according to claim 2,wherein the control unit determines the period in which one or morestill image data pieces generated through the pre-capture function areto be recorded based on an average value and a standard deviation of thedifferences.
 6. The image capture apparatus according to claim 5,wherein the control unit determines, as the period in which one or morestill image data pieces generated through the pre-capture function areto be recorded, a period between the time of the detection of the secondshooting instruction and a time that is backward from the time when thesecond shooting instruction is detected by a sum of the average of thedifferences and a multiple of the standard deviation of the differences.7. The image capture apparatus according to claim 1, wherein in a casewhere the period in which one or more still image data pieces generatedthrough the pre-capture function are to be recorded is equal to orshorter than a predetermined length, the control unit decreases aninterval at which the still image data pieces are generated through thepre-capture function compared to a case where the period in which one ormore still image data pieces generated through the pre-capture functionare to be recorded is not equal to or shorter than the predeterminedlength.
 8. The image capture apparatus according to claim 1, furthercomprising a wireless communication circuit, wherein in a case where thesecond shooting instruction has been received from an external apparatusvia the wireless communication circuit, the control unit corrects thetime of the detection of the second shooting instruction based on adelay amount in wireless communication.
 9. The image capture apparatusaccording to claim 1, wherein in a case where the difference between thetime of the detection of the first shooting instruction and the time ofthe detection of the second shooting instruction is equal to or longerthan a predetermined period, and an interval at which the still imagedata pieces are generated through the pre-capture function is smallerthan a threshold, the control unit increases the interval.
 10. The imagecapture apparatus according to claim 1, further comprising an imageprocessing circuit that executes subject detection processing withrespect to a shot image, wherein in a case where a pre-set subject hasbeen detected as a result of the subject detection processing, thecontrol unit changes a setting of the pre-capture function so as togenerate still image data pieces at a pre-set interval in accordancewith a type of the detected subject.
 11. A control method executed by animage capture apparatus with a pre-capture function for generating stillimage data pieces at a predetermined interval between detection of afirst shooting instruction and detection of a second shootinginstruction, the control method comprising: determining, within a periodin which the pre-capture function was performed, a period in which oneor more still image data pieces generated through the pre-capturefunction are to be recorded in association with a still image data piecegenerated in response to the detection of the second shootinginstruction, based on a difference between (i) a time of the detectionof the first shooting instruction, or a shooting time of an image datapiece selected by a user from among the still image data piecesgenerated through the pre-capture function, and (ii) a time of thedetection of the second shooting instruction.
 12. A non-transitorycomputer-readable medium that stores a program for causing a computerincluded in an image capture apparatus to execute a control method ofthe image capture apparatus, wherein the image capture apparatus has apre-capture function for generating still image data pieces at apredetermined interval between detection of a first shooting instructionand detection of a second shooting instruction, and wherein the controlmethod comprises: determining, within a period in which the pre-capturefunction was performed, a period in which one or more still image datapieces generated through the pre-capture function are to be recorded inassociation with a still image data piece generated in response to thedetection of the second shooting instruction, based on a differencebetween (i) a time of the detection of the first shooting instruction,or a shooting time of an image data piece selected by a user from amongthe still image data pieces generated through the pre-capture function,and (ii) a time of the detection of the second shooting instruction.